Аннотация:The article describes a technical channel of voice information leakage in fiber-optic communications, which is created with parasitic modulation in the light stream that goes through regular connection system. A threat model for voice information is presented with a description of channel operation distinctions. Places and areas of intelligence accessibility are researched and a possible scenario of threat attack is considered. In addition, the article gives recommendations for building an effective system of voice data protection in facilities containing fiber-optic communications.